Rheostat.



NO MODEL.

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William UNITED STATES i rtented .fury 14, 190s. PATENT OFFICE.

WILLIAM C. YATES, OF SCHENECTADY, NEW YORI{,'ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RHEOFSTAT.'

srEcIFrcATIoN forming part' ef Letters :Patent No. 733,610, elated` .my14, 190e'. Application led October 3,1902. Serial No. 125,799. (Nomodel.)

To all whom t may concern:

Be it known that I, WILLIAu C. YATEs,a citizen of the United-States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Rheostats, of which thefollowingis a specification.

This invention relates to a device for regulating the flow of current inany electric cir- Io cuit in which it may be introduced by graduallycutting in and out a resistance-coil which consists of numerous turns ofwire partially embedded in insulating material, but exposed along thepath of a switch-arm. By having the switch-arm move directly over thecoils of the resistance-wire I do away with contactblocks connected tothe wire at intervals, and this enables me to increase or diminish theresist-ance by very small steps. In fact, Inovezo ment of the switch-armcan be made so slight that only one turn of the coil is cut into or outof the circuit, thereby increasing or diminishing the resistance of thecircuitI by only the resistance in one convolution of the wire. On

the other hand, the switch can be moved over the whole length of thecoil, and thus connect into the circuit the entire length of theresistance-wire. In this way I obtain an effective rheostat, simple andeconomical in construc- 3o tion.

In carrying out my invention I provide an electrical conductor in theform of a coil and lay it in a groove in a block of slate or otherlireproof insulator, so that a side of the coil extends slightly abovethe face of the insulating-block. Then I fill the grooves and'thuspartially embed the coil by pouring in such insulation as cement or anyother insulating material which can be introduced in a fluid 4o orplastic condition and which will harden and become solid eithernaturally or by the application of heat. I prefer to use Portlandcement, or a mixture containing the same, for this purpose, not onlybecause it can be used 4 5 in a plastic state and afterward hardened,

but also because it is capable of withstanding a considerable degree ofheat; but I do not limit myself to any particular material, it beingnecessary only that the material used 5o should be an insulator and becapable of being molded into form around the resistancecoil. Thus theembedding substance insulates the portion of each turn oftheresistancewire below its surface from the next-turn and `holds theexposed portions rigidly and a suiii- 5 5 cient distance apart toprevent accidental Vcross connection, and, further, it absorbs much ofthe heat from the surface of the electrical conductor, thereby enablingit to carry a much greater current than it would be ca- 6c pable of Wereitnot so embedded. I prefer to undercut the sides of the groove in theinsulating-block,so as to make the cement more secure in the groove. Aswitch-arm is mounted to move over the exposed portion of the coil andmake electrical contact therewith.

In'order to increase the range of the rheostat, I Iind it convenient toprovide two parallel or concentric coils of wire, each embedded ininsulating material, and aswitch carrying a 7o bridging contact makingcontact with the eX- posed portions of the two coils. Thus any movementof the switch increases or diminishes the length of that portion of eachof the two coils that is connected in the circuit, thereby giving therheostat double the range it would have if only one coil were used. Inthis form of my device I make the two arms of the switch separate, sothat an irregularity in one coil raising the switch-arm bearing on 8othat coil would not raise the other switch-arm oif the other coil.

In the accompanying drawings I have shown an embodiment of my inventionhaving two coils and a two-armed switch making contact therewith.

Figure l is a top plan view; Fig. 2, a side elevation 3 and Fig. 3, across-section along the line :I: or., showing the partially-embeddedcoils. 9o

A is a base-block, preferably of slate or other insulating and heatabsorbing substance, having two circular concentric grooves B B cut inits upper surface. These grooves are preferably undercut, as indicated.On the under side of the base are mounted terminals M and N, extendingthrough the plate to corresponding points in the grooves B B,respectively. In each of these grooves is placed lengthwise a continuoushelical coil Ioo of wire C C of predetermined resistance, one side ofeach coil extending slightly above the surface of the `block A. Thecoils C C' are connected at one end to the upper ends of the terminals Mand N, respectively, and from these terminals they extend almost aroundthe grooves B B, being connected at their extremities to the upper endsof metallic studs M N, respectively. These studs are mounted on theunder side of the block A and extend through the grooves B B. They areconnected on the under side of the base by the wire h, so that thecircuit will not be broken if one of the switch-arms is raised oit' thecoil. The grooves 'B B are iilled with a suitable insulating-cement orother insulating heat-absorbing material, so that the coils C G areembedded in insulation except for the side which extends above the faceof the base A.

D D are spring switch-arms adapted to bear down on the exposed sides ofthe coils C C. They are mounted one directly over the other andelectrically connected at the handle E, which is pivoted at the centerof the circular grooves. Contact between the coils might be made by asimple bridging-brush mounted on the end of an arm lixed to the handle;but I prefer the construction shown, since it admits of independentpressure on each helix, and thus prevents poor contact if the wearshould be uneven or if one or more turns in either helix should be bentor otherwise damaged.

F is a stud set in the base A between the spaces between the ends of thecoils and the pivot of the handle to prevent the switcharm from passingfrom one end of the coils to the other without moving over their entirelength.

The rheostat is connected in the circuit at M and N. In the positionshown in Fig. l the current enters at M and goes to the coil C, alongthe switch D, back over the switcharm D and the coil C to the contact N.In this position the resistance is nil. As the switch is moved over thecoils it cuts into the circuit successive convolutions of the coils overwhich it passes, vfor then the current has to pass along the coil C fromM to the arm D and along the coil C from arm D to N. IVhen theswitch-arms have been turned completely around to the extreme positionresting against the stud F, the entire length of each coil is in thecircuit, and the current passes from one coil to the other through theswitch-arms or over the wire 7L.

IVhat I claim as new, and desire to secure by Letters Patent of theUnited States, is-

l. A rheostat having a coil or coils of`wire embedded lengthwise ininsulation so that the convolutions are exposed along one side ol thecoil or coils, and a switch-arm makin g contact with the exposedportion.

2. A helical coil of wire, the convolutions of which are surrounded withinsulating material, except on an exposed side and a switcharm adaptedto move over and make contact with the exposed portions of saidconvolutions.

3. In a rheostat,in combination with a base, a coil or coils of wiresunk lengthwise in insulation so that a portion of each convolutionextends above the insulation and is exposed, and a switch adapted tomove over and make contact with the exposed part of said coil or coils.

4. A rheostat having resistance-wire coiled in the form of a helix andsunk in an insulating substance so as to leave one side of the coilexposed, and a switch-arm adapted to move over and make -contact withsaid exposed portion.

5. A rheostat having two resistance-wires coiled and embedded lengthwisein insulating material so that a portion of the coils extends above theinsulating material and is exposed, and a two-armed switch adapted tomove over and make contact with the exposed portion of said coils.

i5. A rheostat having two resistance-wires coiled and embeddedlengthwise in insulating` material so that a portion of the coilsextends above the insulating material and is exposed, and a bridgingdevice adapted to move over and make contact with the exposed portion ofsaid coils.

7. In a rheostat, two wire helices laid in concentric grooves andpartially embedded in linsulating material, and means for making contactwith the exposed portion of said helices.

S. A plurality of wire helices supported in insulating material andsurrounded thereby except along an exposed side of each helix, andcontact-bril shes making contact with said exposed sides to vary theresistance in circuit.

A plurality of wire helices supported in insulating material andsurrounded thereby except along an exposed side of each helix, and acontact device making contact with said exposed sides to vary theresistance in circuit.

10. In a rheostat, two wire hel ices connected IfO IIO

at one end, an insulating substance inclosing said wire except along anexposed side of each helix, and a contact device making contact with theexposed sides to vary the resistance in circuit.

In witness whereof I have hereunto set my hand this 2d day of October,1902.

IVILLIAM C. YATES. Iitnessesz BENJAMIN B. HULL, HELEN ALFonD.

